Etch Figure On Quartz Crystal Formed By KOH And NaOH Solution And Its Difference From That Formed By HF Solution

Quartz, SiO2 point group 32 (L33L2) is a kind of mineral which is very common in the nature. The etch figure of quartz is formed by acid or alkali's erosion on the crystal face and manual section. There is a long history of etch figure's research. The earliest research is in mineral field. During those time, people use the natural or artificial etch figure of crystal to study crystals'symmetry and twins. However, this kind of application is not paid attention by people these days, because of modern invention of diffraction technologies. Although etch figure is an efficient channel to orientate the crystal and distinguish the twins and reflect the character of symmetry precisely and deeply, the connection between these characters and theory of symmetry is not known. So this way isn't applied in the geology widely.In this article, we choose a-quartz crystal which has deep sense on geology to study and, use KOH solution and NaOH solution to try the experiments.We observe the etch figures on the crystal faces and sections which have different implications for crystallography after eroding of alkali by using DIC and AFM. After observing and studying natural crystal faces including hexagonal prism face{1010}, rhombohedron positive face_{1011}, negative face{0111}and manual section including trigonal prism face{1120},{2110}, we find that same simple forms' crystal faces or sections have the same etch pits, and etch pits on the different simple forms have different characters.The shape of etch pit on the positive form and negative form of the same simple form is also different. So, we can connect the symmetric characters of crystals and symmetric theories through the 3D distribution projection of etch pit formed by eroding by KOH on the quartz face and section.Additionally, different kinds of corrosive may produce different etch figures on the same crystal face, in which people don't have deep study. Although there are differences between etch figures formed by acid and alkali, they still show the inherent symmetry of L33L2.This research can reveal the symmetry of crystal and also reveal the referential meaning of minerals that exit in the acidity or alkaline geology environment.